1. Technical Field
The present invention relates to a technique to superimpose dots of special ink on at least some of dots of ordinary ink.
2. Related Art
Hitherto, in the field of electrophotography, there has been proposed a technique in which, for an area with respect to which metallic color is specified, a solid layer of metallic toner is formed and then a fine or coarse process color toner layer is formed on it (see JP-A-2006-50347). In this technique, by superimposing a process color toner layer on a metallic toner layer, various tones of metallic color are reproduced.
Color printing techniques using toner include a tandem method and a four-cycle method. In both methods, printing is performed by superimposing respective colors of toners. Therefore, it is relatively easy to superimpose process color toner on metallic toner.
However, in the field of ink jet printers, respective colors of inks are ejected almost simultaneously from a head onto a printing medium, and thereby printing is performed. Therefore, if a special ink, such as a metallic ink, and an ordinary color ink are ejected simultaneously, the inks are mixed on a printing medium, and intended gloss and color cannot be obtained. To avoid such a problem, it is possible to divide the ink jet printing process into a process of printing in special ink and a process of printing in ordinary ink and to superimpose them. However, this can cause new problems such as decrease in printing speed, increase in man-hour, and misalignment between the first printing and the second printing.